1. Field of the Invention
The present invention provides a backlight module, and more particularly, relates to a backlight module utilized in a liquid crystal display (LCD) such that high transmittance and sufficient brightness are achieved.
2. Description of the Prior Art
A typical prior art liquid crystal display comprises a transparent electrode pair, a liquid crystal layer disposed between the transparent electrode pair, and two polarizers disposed on a front side and a back side of the liquid crystal display. The liquid crystal display usually comprises a light source for emitting white light. In order to present different colors red color filters, green color filters, and blue color filters, patterned in a mosaic or patterned in a stripe, are formed on a surface of the transparent electrode pair in the prior art liquid crystal display. When liquid crystal molecules in the liquid crystal layer are affected by a potential difference between the transparent electrode pair to align in a specific state, the white light emitted from the light source penetrates the liquid crystal layer and reach each of the color filters. Each of the color filters allows red light, green light, or blue light, all having different wavelengths from each other, to pass to produce color images.
Please refer to FIG. 1, which is a structural schematic diagram of a liquid crystal display 10 according to the prior art. The prior art liquid crystal display 10 comprises a backlight module 12 for emitting white light 13, a first polarizer 14 for screening light having a specific orientation from the white light 13 emitted from the backlight module 12, and a second polarizer 16 for receiving light having the specific orientation screened by the first polarizer 14. A first transparent substrate 18 composed of transparent materials, such as glass and other materials; a first transparent electrode 20 composed of indium tin oxide (ITO); a liquid crystal layer 22; a second transparent electrode 24; an overcoat layer 26 composed of transparent resin; a color filter layer 28 constituted by red color filters 28R, green color filters 28G, and blue color filters 28B; and a second transparent substrate 30 are disposed, from bottom to top, between the first polarizer 14 and the second polarizer 16. The red color filters 28R, the green color filters 28G, and the blue color filters 28B are arranged with regularity and a position of each of the color filters corresponds to a position of each of a plurality of pixel electrodes (not shown) arranged in array on the first transparent electrode 20. A light-impermeable layer 32 is provided between the adjacent color filters.
The prior art liquid crystal display 10 utilizes a cold cathode fluorescent light lamp (CCFL) as a backlight module 12. Invisible light having a wavelength shorter than approximately 400 nm is first produced by the backlight module 12 before being transformed into white light 13. During the transformation, energy loss readily occurs. Moreover, the energy loss problem becomes serious when white light 13 emitted from the backlight module 12 passes through the red color filters 28R, the green color filters 28G, or the blue color filters 28B to respectively display red light 34R, green light 34G, or blue light 34B because only a portion of light having a specific wavelength can pass through each of the red color filters 28R, the green color filters 28G, and the blue color filters 28B. The intensity of red light 34R, green light 34G, and blue light 34B passing through each of the red color filters 28R, the green color filters 28G, and the blue color filters 28B respectively is reduced by over one third of the intensity of the white light 13 emitted from the backlight module 12. Therefore, the prior art liquid crystal display 10 has the problems of low transmittance and insufficient brightness.